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PGI Kolloquium:

Prof. Dr. Artur Zrenner,
Paderborn University, Paderborn , Germany

PGI Lecture Hall, Building 04.8, 2nd Floor, Room 365

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13.07.2018 11:00 Uhr

Coherent Optoelectronics with Single Quantum Dots

In optical experiments on single quantum dot photodiodes the exciton ground state transition appears as a two-level system with a lifetime limited line width of a few µeV. For the case of pulsed laser fields and in the absence of decoherence, the ground state exciton represents a quantum bit (qubit), which can be also tuned by electric fields. Using fast electric signals, which are phase-locked to ps-laser pulses, the coherent control of an exciton qubit can be obtained by electric switching [1].

Copyright: Prof. Dr. Zrenner

For the coherent electric control of InGaAs quantum dots we have developed ultrafast SiGe-BiCMOS chips, which are designed for low temperature operation. With this technology electric pulses with rise times below 20 ps become available for the transient laser-synchronous Stark tuning of quantum dots.

Performing Ramsey experiments [2] we have been able to demonstrate the electric phase control of a quantum dot exciton on sub-100 ps timescales [3]. Based on this we propose a protocol, which allows full control of the exciton Bloch vector by solely electric control.

In the past, the robust inversion of quantum dots has been demonstrated by applying chirped ps laser pulses, which drive a rapid adiabatic passage [4, 5]. An ultrafast electric transient results in a transient Stark shift and hence in a chirp of the ground state transition. Realizing such conditions, we have been able to drive a rapid adiabatic passage using electric chirp but un-chirped laser pulses. A comparison to Rabi oscillations observed for increasing pulse areas shows that the electrically chirped rapid adiabatic passage leads to full inversion.